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From: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-trace-devel@vger.kernel.org
Subject: Re: [PATCH v19 03/15] trace-cmd: Find and store pids of tasks, which run virtual CPUs of given VM
Date: Thu, 27 Feb 2020 10:30:56 +0200
Message-ID: <CAPpZLN4DGDXxJZ0zsgRDcohKiBdgURUOik+O6hR4Fi1Gx9MsBg@mail.gmail.com> (raw)
In-Reply-To: <20200226231314.5d4a6e5f@oasis.local.home>

On Thu, Feb 27, 2020 at 6:13 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Fri, 31 Jan 2020 14:10:59 +0200
> "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:
>
> > From: Tzvetomir Stoyanov <tstoyanov@vmware.com>
> >
> > In order to match host and guest events, a mapping between guest VCPU
> > and the host task, running this VCPU is needed. Extended existing
> > struct guest to hold such mapping and added logic in read_qemu_guests()
> > function to initialize it. Implemented a new internal API,
> > get_guest_vcpu_pid(), to retrieve VCPU-task mapping for given VM.
> >
> > Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com>
> > ---
> >  tracecmd/include/trace-local.h |  2 ++
> >  tracecmd/trace-record.c        | 54 ++++++++++++++++++++++++++++++++++
> >  2 files changed, 56 insertions(+)
> >
> > diff --git a/tracecmd/include/trace-local.h b/tracecmd/include/trace-local.h
> > index 29f2779..a5cf064 100644
> > --- a/tracecmd/include/trace-local.h
> > +++ b/tracecmd/include/trace-local.h
> > @@ -247,6 +247,8 @@ void update_first_instance(struct buffer_instance *instance, int topt);
> >
> >  void show_instance_file(struct buffer_instance *instance, const char *name);
> >
> > +int get_guest_vcpu_pid(unsigned int guest_cid, unsigned int guest_vcpu);
> > +
> >  /* moved from trace-cmd.h */
> >  void tracecmd_create_top_instance(char *name);
> >  void tracecmd_remove_instances(void);
> > diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
> > index 28fe31b..b479e91 100644
> > --- a/tracecmd/trace-record.c
> > +++ b/tracecmd/trace-record.c
> > @@ -3031,10 +3031,12 @@ static bool is_digits(const char *s)
> >       return true;
> >  }
> >
> > +#define VCPUS_MAX 256
> >  struct guest {
> >       char *name;
> >       int cid;
> >       int pid;
> > +     int cpu_pid[VCPUS_MAX];
>
> Although this is probably fine for the near future, I don't like
> arbitrary limits that don't have to do with max sizes of the storage
> unit (like max int).
>
> Why is the cpu_pid a static array and not one that is allocated? We
> could use realloc, couldn't we, in the loading of it?
>

I did it to simplify the PoC implementation and never changed it to be
a dynamic array,
I'll reimplement it now.
Thanks Steven!

> -- Steve
>
> >  };
> >
> >  static struct guest *guests;
> > @@ -3052,6 +3054,43 @@ static char *get_qemu_guest_name(char *arg)
> >       return arg;
> >  }
> >
> > +static void read_qemu_guests_pids(char *guest_task, struct guest *guest)
> > +{
> > +     struct dirent *entry;
> > +     char path[PATH_MAX];
> > +     char *buf = NULL;
> > +     size_t n = 0;
> > +     int vcpu;
> > +     DIR *dir;
> > +     FILE *f;
> > +
> > +     snprintf(path, sizeof(path), "/proc/%s/task", guest_task);
> > +     dir = opendir(path);
> > +     if (!dir)
> > +             return;
> > +
> > +     while ((entry = readdir(dir))) {
> > +             if (!(entry->d_type == DT_DIR && is_digits(entry->d_name)))
> > +                     continue;
> > +
> > +             snprintf(path, sizeof(path), "/proc/%s/task/%s/comm",
> > +                      guest_task, entry->d_name);
> > +             f = fopen(path, "r");
> > +             if (!f)
> > +                     continue;
> > +
> > +             if (getline(&buf, &n, f) >= 0 &&
> > +                 strncmp(buf, "CPU ", 4) == 0) {
> > +                     vcpu = atoi(buf + 4);
> > +                     if (vcpu >= 0 && vcpu < VCPUS_MAX)
> > +                             guest->cpu_pid[vcpu] = atoi(entry->d_name);
> > +             }
> > +
> > +             fclose(f);
> > +     }
> > +     free(buf);
> > +}
> > +
> >  static void read_qemu_guests(void)
> >  {
> >       static bool initialized;
> > @@ -3115,6 +3154,8 @@ static void read_qemu_guests(void)
> >               if (!is_qemu)
> >                       goto next;
> >
> > +             read_qemu_guests_pids(entry->d_name, &guest);
> > +
> >               guests = realloc(guests, (guests_len + 1) * sizeof(*guests));
> >               if (!guests)
> >                       die("Can not allocate guest buffer");
> > @@ -3160,6 +3201,19 @@ static char *parse_guest_name(char *guest, int *cid, int *port)
> >       return guest;
> >  }
> >
> > +int get_guest_vcpu_pid(unsigned int guest_cid, unsigned int guest_vcpu)
> > +{
> > +     int i;
> > +
> > +     if (!guests || guest_vcpu >= VCPUS_MAX)
> > +             return -1;
> > +
> > +     for (i = 0; i < guests_len; i++)
> > +             if (guest_cid == guests[i].cid)
> > +                     return guests[i].cpu_pid[guest_vcpu];
> > +     return -1;
> > +}
> > +
> >  static void set_prio(int prio)
> >  {
> >       struct sched_param sp;
>


-- 
Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center

  reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-31 12:10 [PATCH v19 00/15]Timestamp synchronization of host - guest tracing session Tzvetomir Stoyanov (VMware)
2020-01-31 12:10 ` [PATCH v19 01/15] trace-cmd: Add support for negative time offsets in trace.dat file Tzvetomir Stoyanov (VMware)
2020-01-31 12:10 ` [PATCH v19 02/15] trace-cmd: Add new library API for local CPU count Tzvetomir Stoyanov (VMware)
2020-01-31 12:10 ` [PATCH v19 03/15] trace-cmd: Find and store pids of tasks, which run virtual CPUs of given VM Tzvetomir Stoyanov (VMware)
2020-02-27  4:13   ` Steven Rostedt
2020-02-27  8:30     ` Tzvetomir Stoyanov [this message]
2020-01-31 12:11 ` [PATCH v19 04/15] trace-cmd: Implement new API tracecmd_add_option_v() Tzvetomir Stoyanov (VMware)
2020-01-31 12:11 ` [PATCH v19 05/15] trace-cmd: Add new API to generate a unique ID of the tracing session Tzvetomir Stoyanov (VMware)
2020-01-31 12:11 ` [PATCH v19 06/15] trace-cmd: Store the session tracing ID in the trace.dat file Tzvetomir Stoyanov (VMware)
2020-01-31 12:11 ` [PATCH v19 07/15] trace-cmd: Add definitions of htonll() and ntohll() Tzvetomir Stoyanov (VMware)
2020-01-31 12:11 ` [PATCH v19 08/15] trace-cmd: Exchange tracing IDs between host and guest Tzvetomir Stoyanov (VMware)
2020-01-31 12:11 ` [PATCH v19 09/15] trace-cmd: Implement new option in trace.dat file: TRACECMD_OPTION_TIME_SHIFT Tzvetomir Stoyanov (VMware)
2020-02-27  3:49   ` Steven Rostedt
2020-01-31 12:11 ` [PATCH v19 10/15] trace-cmd: Add guest information in host's trace.dat file Tzvetomir Stoyanov (VMware)
2020-02-27  3:53   ` Steven Rostedt
2020-02-27  3:56   ` Steven Rostedt
2020-02-27  9:39     ` Tzvetomir Stoyanov
2020-01-31 12:11 ` [PATCH v19 11/15] trace-cmd: Add host trace clock as guest trace argument Tzvetomir Stoyanov (VMware)
2020-01-31 12:11 ` [PATCH v19 12/15] trace-cmd: Refactor few trace-cmd internal functions Tzvetomir Stoyanov (VMware)
2020-01-31 12:11 ` [PATCH v19 13/15] trace-cmd: Basic infrastructure for host - guest timestamp synchronization Tzvetomir Stoyanov (VMware)
2020-01-31 12:11 ` [PATCH v19 14/15] trace-cmd: [POC] PTP-like algorithm " Tzvetomir Stoyanov (VMware)
2020-01-31 12:11 ` [PATCH v19 15/15] trace-cmd: Debug scripts for " Tzvetomir Stoyanov (VMware)

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